This vintage Bianchi has 24 inch wheel, 50cm seat tube and 53cm top tube. I have not seen the bike, just images. Any idea what size person it would suit?

Shorter than 5'.

Looks more like a 52cm seat tube, given steerer tube height. Best for 5'4"-5'6"

Thanks for the info.
A couple of inches too short for me. I find it difficult to get vintage bikes in my size, I am 5'7ish and inseam is 30". Most vintages I have seen are way bigger. I was looking at a 54x54 Motobecane but the standover height was 31" so it wouldn't work for me. Modern bikes work ok because of the sloping top tube. So I guess I am looking at a 52 seat tube and 52 - 54 Top tube or thereabouts, but I'm not finding any.

You are correct about the seat tube, it is 50 centre to centre, so probably 2 extra cm to the top.

Learn to IGNORE stand over on sizing. Get a top tube length that fits you and you will do fine.

Also, vintage bikes tended to take bigger jumps between sizes. Many brands went 2 full inches between sizes, which equals 5cm! Your target is way too narrow. And I don't see 52cm ST very often at all. Much more common is the 21 inch frame size, which is 53cm. I've owned well over 600 bikes, probably 100 were 53cm seat tube. I don't recall ever owning a single 52cm seat tube bike (sure, they are out there, but not very common). I find a lot of 23 inch seat tube bikes, some 21 inch, some 22 and 24 inch (some manufacturers went 22/24/26 inch frame sizes). Then a handful of 25 inch/25.5 inch and 19 inch. I've had three 18 inch (really rare).

Seat tube sizing by most manufacturers measured center to top.

And on TT length, realize you can play around with stem length to compensate for too long or too short TT. Sure, you want to be close, but a 2cm range is only about 3/4 of an inch.

FWIW, my inseam is 30 inches and I ride a 56/57. I pretty much have negative standover on every road bike I own, but I have a long torso and arms. I have a dual sport motorcycle with a 36 inch seat height. Talk about a stretch!

Size via TT length and you will find plenty.

Thanks, most helpful. As you can see I'm new to this. Took up cycling a couple of years ago. I will be 50 soon. I would like to get something like I had as a kid. I used to have a Puch Pacemaker and an Eddie Merckx branded bike (from research this probably was a falcon). We are talking around late 70's. Obviously they were junior size bikes then, but I hope to get something from that era, probably something cheap and cheerful, a winter project, and try to learn about restoration on it. That Bianchi is pretty low end, but could be made pretty, will never be made fast!!

For what it's worth, I wear a pants with a 30" inseam and stand 5'8". A perfect fit for me is 55cm C-T with a comparable top tube length -- both Capos and the Bianchi. Echoing the "forget seat tube length" suggestion, I rode a 23" C-T Nishiki for many years. I could barely straddle it, but it had such a short top tube that I needed to get a longer-reach stem. Conversely, my 57cm Peugeot PKN-10 was so long in the top tube that I needed a minimum-reach stem, which did not look great, but which made the bike fit me fairly well.